1. Field of the Invention
The present invention relates to an apparatus and method for purifying sewage and wastewater, and, more particularly, to an apparatus and method for purifying sewage and wastewater, which can remove 90% or more of nitrogen and phosphorus from sewage and wastewater.
2. Description of the Related Art
Generally, conventional technologies for purifying highly concentrated persistent organic wastewater are based on a standard activated sludge process. Using the conventional technologies, a considerable amount of organic matter and suspended solids included in wastewater can be removed, but eutrophication and red tide phenomena occur because nitrogen and phosphorus, which are nutritive salts, are not easily removed from wastewater. Further, in the conventional technologies, nitrogen is removed using a method of nitrifying nitrogen, creating an anaerobic or anoxic state, and then expelling any remaining air, and phosphorus is removed using a method of inducing the discharge of phosphorus by creating an anaerobic state, making microbes ingest excess phosphorus while converting the anaerobic state into an aerobic state, and then dewatering sludge together with phosphorus. However, in the above methods, the efficiency of nitrogen and phosphorus removal is in the range of 50 to 60% or less, continuously stable water quality cannot be obtained because the process is sensitive to decreases in water temperature and to variation of water quality and the amount of water, and highly advanced technical skills are required to operate the equipment because a large amount of power is necessary to nitrify nitrogen and the processes are complicated. Further, the above methods have problems in that equipment for removing bad smells generated in each process must be additionally installed, and the equipment has a short life because it easily corrodes, and the cost of maintaining the equipment is high.
Among conventional biological processes for treating sewage and wastewater, processes using rotary disks are commonly used, but in most of the processes modified plastic plates are used as a contactor of microbes.
An initial rotary disk type contactor has good purification efficiency because a large amount of biofilm adheres to the contactor when it is immersed in a sewage and wastewater tank in the range of about 30%, but simultaneously has both aerobic and anaerobic states because oxygen is not constantly supplied to the biofilm adhered to the rotary disk and the contactor is not uniformly in contact with inflowing sewage and wastewater. Accordingly, the initial rotary disk contactor has problems in that purification efficiency decreases because the activity of microbes for purification is hindered, bad smells are generated while the separation phenomenon occurs, and the contactor frequently breaks down because the biofilm irregularly adheres to the contactor, and thus the contactor does not rotate normally.
Conventional technologies for purifying sewage and wastewater using a rotary disk will be described as follows.
Korean Patent No. 0276095 discloses an apparatus and method for purifying sewage and wastewater using Bacillus species bacteria, in which sewage and wastewater, and microbes and Bacillus activator, including Bacillus species bacteria as a main component, are put into a rotary microbe contact tank, and then a porous rotator formed of synthetic fiber is rotated in a state in which the rotator is partially immersed in sewage and wastewater.
However, the rotary microbe contact tank has disadvantages in that, since the thickness of the biofilm adhered to the fiber is thin, the efficiency of sewage and wastewater purification is decreased when the temperature of inflowing sewage and wastewater is decreased, and the recovery time is long when apparatuses break down or there is an aberration in the culture of microbes during a sewage and wastewater purification process. Further, there is a problem in that since a rotary activated bacillus contactor has low durability, the rotary activated bacillus contactor is easily deformed and damaged, and thus the entire rotary activated bacillus contactor must be replaced in order to repair the damaged contactor.